Method and apparatus for calipering



Oct. 4, 1955 R. F. MONTGOMERY EIAL 2,719,362

METHOD AND APPARATUS FOR CALIPERING Filed Dec. 9, 1952 4 Sheets-Sheet 1 NVE TORS flmme/i UM 1955 R. F. MONTGOMERY ETAL 2,719,362

METHOD AND APPARATUS FOR CALIPERING 4 Sheets-Sheet 2 ivENToRs ATTORNEYS Filed Dec. 9, 1952 ct. 4, 1955 R. F. MONTGOMERY ETAL 2,719,362

METHOD AND APPARATUS FOR CALIPERING ATTORNEYS Oct. 4, 1955 R. F. MONTGOMERY ETAL 2,719,362

METHOD AND APPARATUS FOR CALIPERING INVENTORS 4 SheetsSheet 4 Filed Dec. 9, 1952 ATTORNEYS United States Patent METHOD AND APPARATUS FOR CALIPERING Richard Franklin Montgomery, Snyder, and Nicolaas L. H. Koot, Odessa, Tex.

Application December 9, 1952, Serial No. 324,982

22 Claims. (Cl. 33-178) Our invention relates to the art of calipering a well bore, and more specifically provides a novel method of running the caliper and novel apparatus for carrying out said method.

The principal object of our invention is to provide a novel and greatly improved method of running a caliper within a drilled bore. It is well known that the removal of a drill string from a bore several miles deep is a timeconsuming operation which in itself contributes relatively little information to the operators. In all known methods now used, when the bore is completed, it is necessary to pull all of the drill string out of the bore and then to run a caliper down into the bore on a wire line, the log generally being recorded on the surface by the aid of electronics. According to the present invention, however, we use a survey bit on the lower end of the drill string, such bit having a hole therethrough communicating with the drill string passage, When the drilling operation has been completed and the desired depth of bore established, the operator then opens the kelly joint and inserts our novel recording tool and swivel support into the pipe string and pumps these members downwardly in the string until they reach and enter the survey bit. The recording tool passes through the hole in the lower end of the bit and is suspended by the swivel support below the bit, the swivel support having a ball bearing ring which engages the bit, and rotatably maintains the recording assembly suspended therebelow. At the lower end of the recording tool are secured a plurality of caliper arms to pivot outwardly and engage the walls of the bore as soon as the tool has cleared the lower end of the survey bit. When the recording tool is thus operatively suspended below the bit, caliper arms will record on a chart within the tool a running log of the size of the bore as the drill string assembly is moved upwardly within the bore during removal of the drill string therefrom. When the assembly has been entirely withdrawn from the drilled bore, the recording tool is recovered and the operator removes the chart whereon is graphically inscribed the running log of the diameter of the bore.

An important feature of novelty of our invention relates to the above-mentioned pumping of the recording tool downwardly through the drill string whereby said tool travels in a smooth bore all the way down so that the caliper arms are protected from damage. This feature also eliminates the possibility of the tool sticking or getting lodged or hung up as it travels downwardly. The tools of the prior art when lowered on a wire line into the bore have a tendency to encounter irregularities within the bore and bridge thereacross, particularly when the bore drilled into the earth is not straight.

A further object of our invention is to provide a method and apparatus for calipering a bore which can be used with a standard drill string and a standard survey bit, no changes therein being necessary.

Another object of this invention is to provide a swivel support assembly through which continuous fluid circulation may be maintained to enable the operator to main- "ice tain control of the bore against blowouts during the calipering operation.

Another object of our invention is to provide a swivel tool-support having a piston and cylinder structure in its upper end, the piston being maintained in the cylinder by shear pins so that as the support is seated in the survey bit, the piston will block a fluid duct through the support and cause a sudden pressure rise in the drill string thereby warning the operator on the surface of the arrival of the caliper assembly in the survey bit. When the pressure in the string has risen to a level sufiicient to break the shear pins, the piston will be released to move out of the duct through the tool support and a sudden drop in pump pressure and resumption of normal circulation will inform the operator that the support and caliper assembly is positioned ready to begin the calipering oper ation.

Still another object of my invention is to provide a rotational engagement between the tool support and the bit so that when the caliper arms are engaging the walls of the bore, the pipe string may be rotated by the operator for the purpose of disconnecting the stands of pipe as they are withdrawn from the bore, said rotational engagement allowing the caliper arms to stand motionless against the well bore during such rotation of the pipe string.

A further object of our invention is to provide a universal joint between the lower end of the swivel support and the upper end of the caliper tool to permit the tool to position itself as may be required to pass through a crooked portion of the bore.

Another important object of our invention is to provide a telescoping engagement between the survey bit and the swivel support whereby the caliper arms will not be damaged in the event the pipe string should be lowered through a short distance as the tool joints are unscrewed at the surface during disconnecting of the successive stands of pipe.

Another primary object of our invention is to provide an hydraulic recording tool adapted to be suspended below the survey bit and having a plurality of caliper arms pivoted to its lower end, each arm having a cam surface which engages an associated cam follower, said cam followers being moved by said arms in accordance with the variation of the pivotal position of the arms as they travel upwardly within the bore constantly contacting the varying inside contour thereof. Each of these cam followers is operatively connected to an associated measuring piston acting upon a confined liquid within the recording tool. The total volume of space occupied by the confined liquid is always a constant and the respective measuring pistons, as they are moved by the associated cam followers, cause the distribution of the fluid on each side of a separate recording piston to fluctuate, thereby driving the recording piston upwardly or downwardly within the recording tool in accordance with the instantaneous summation of the positions of all of the meas-- uring pistons. The recording piston is linked to a recording stylus, which stylus presses against a moving chart and records thereon the average diameter of the well bore in accordance with the summation of the readings supplied by all of the aforementioned caliper arms, the moving chart being driven by a clock mechanism contained within the recording tool.

The advantage of this assembly is that the log of the diameter of the well bore may be accurately obtained because of the fact that the various caliper arms work in dependently of each other and because of the fact that the hydraulic recording system provides a reading which is proportional to the summation of the instantaneous positions of all of the arms. Thus, if the well bore is crooked and the caliper is lying against one side of the bore so that the caliper arms are fully retracted on that side, the arms opposite the side of the caliper contacting the well bore will be further expanded to compensate for the fact that the caliper is not centered within the bore at that particular moment.

Another important advantage of the present. invention is that static-electric charges within the bore will not afiect the readings of the recording tool, since the latter operates by mechanical and hydraulic means rather than by electrical recording means.

Other objects and advantages of our invention will become apparent during the discussion of the drawings, wherein:

Fig. l is a section through a well bore, showing a drill string including a standard survey bit at its lower end.

Fig. 2 is a section through the well bore showing the drill string pulled upwardly through a distance sufficient to permit the swivel support, caliper tool and caliper arms to be suspended below the survey bit, the bit being shown in cross-section and the figure showing the caliper arms extended outwardly and engaging the walls of the bore.

Figs. 3, 3a, and 3b illustrate sections through the swivel support and through the caliper tool and arms, the latter being shown in retracted position.

Figs. 4, 4a, and 4b illustrate other sections through the recording tool, showing the cam followers connected with the measuring pistons, and contacting the cams on the caliper arms and showing the chart drums operatively engaged with the clock and drive mechanism, the latter being illustrated only schematically.

Fig. 5 is a section view taken along line 55 of Fig. 4, and showinga chart mounted on the rollers.

Fig. 6 is a section view along line 6-6 of Fig. 4.

Fig. 7 is a section view along line 77 of Fig. 4a.

Fig. 8 is a section view along line 8-8 of Fig. 3b.

Fig. 9 is a section view along line 99 of Fig. 3b.

Fig. 10 is a section view along line 1010 of Fig. 3b.

Fig. 11 is a section view along line 11-11 of Fig. 3b.

Fig. 12 is a section view along line 1212 of Fig. 3b.

Fig. 13 is a section view along line 1313 of Fig. 3b.

Referring now to the drawings, Figs. 1 and 2 illustrate a bore B having a drill string S suspended therein. The drill string carries at its lower end a survey bit D, having a centrally located hole H therethrough tapering upwardly into the fluid passage P of the drill string along a tapered portion T. These members form no part of the present invention.

The swivel support As shown in Figs. 2 and 3 We have provided a swivel support 1 having an elongated rod 1a enlarged at its upper end 1b and having a cylinder 10 in its upper end, this cylinder communicating at the upper end of the rod 1a with the fluid passage P in the drill string by means of small ducts 1d and said cylinder 10 communicating with the bore B via a plurality of small ducts 1e. The upper end of the rod 1a may also be provided with a fishing tip 1].

Within the cylinder 10 we have provided a piston 1h which is normally retained at the upper end of the cylinder 10 by means of shear pins 2 for the purpose hereinafter stated. At the lower end of the cylinder 10 is a small vent 1k to permit the escape of fluid trapped between the ducts 1e and the vent 1k when the piston 1h travels downwardly toward the bottom of the cylinder 10. The purpose of the piston and cylinder arrangement will be hereinafter discussed.

Near the upper end of the rod 1a is a ring 3 rotatably retained between the enlarged portion 1b of the rod 1a and a threaded retaining member 4, the ring 3 being maintained in place therebetween by annular series of ball bearings 3a. By reference to Fig. 2 it will be seen that the outer periphery 3b of the ring 3 is larger than the hole H through the survey bit so that the ring 3 will normally engage the tapered portion T within the survey bit to rotatably suspend the swivel support thereon.

At the lower end of the rod 1a we provide a universal ball joint 5' said joint including a ball 5a threadedly secured to the lower end of the rod 1a as at 5b, the ball being provided with a wrench socket 5c in its lower end to facilitate the tightening of the threaded joint 5b. The ball joint 5 also includes a seat 5d maintained in tight engagement with the ball 5a by a block 5e pressed against the ball 5a by a spring 5 The spring may be compressed and secured in place by a screw plug 5h as shown in Fig. 3. The lower end of the universal joint 5 is externally threaded as at SS which threads engage complementary threads 6a in the upper end of the recording tool 6.

The recording tool By reference to the drawing, Figs. 3a, 3b, 4, 4a, and 4b it will be seen that at the lower end of the recording tool 6 are a series of downwardly extending cam followers 7. Above the cam followers 7 and fixed thereto are measuring pistons 7a, each of the pistons 7a having an upward ly extending connecting rod 7b screwed into an upper measuring piston 70, and each of the connecting rods 7b passing through a sleeve 74 secured against'longitudinal displacement by means of a set screw 7e. Above each measuring piston is a compressed coil spring 9, which spring operates to press the associated piston 70 downwardly within its associated cylinder 6b, which cylinder is vented outside of the body of the recording tool 6 as at the vent 60.

By reference to Fig. '9 it will be seen that the space within the cylinders 6b and lying between each sleeve 7d and each lower measuring piston "in is connected with a longitudinal duct 67c by means of short ducts 611 Similarly, in Fig. 8 it will be seen that the space within the cylinders 6b and lying between each sleeve 7d and each upper measuring piston 70 is connected with the axial duct 6d by means of a plurality of short ducts 6e.

Figs. 4 and 4a show that the cylinders 6b and the ducts 60!, 6e, 6k, and 6m are filled with a liquid. This liquid presses against the lower end of a recording piston 10 in duct 6k, and also presses against the upper end of the recording piston 10 as at 6r, Fig. 4.

It should now be apparent that when a cam follower 7 is moved upwardly, the volume below the associated pistons 70 (and therefore the volume of liquid within the ducts 6d and 62) will be increased, and that by the same movement the volume of liquid within the cylinder 61) above the pistons 7a, (and therefore in the ducts 6m and 6k) will be decreased so that the liquid will press against the lower end of the recording piston 10 and move it upwardly. Conversely, when the cam follower 7 is moved downwardly the liquid will press against the upper end of the recording piston 14; at 6r and drive the latter downwardly.

Figs. 8 and 9 show that all of the cylinders 6b are connected together both in the vicinity of the ducts 6e and in the vicinity of the ducts 6m, and therefore the amount of motion transmitted to the recording piston 10 by the liquid will be proportional to-the instantaneous summation of the movement up or down of all of'the cam followers 7.

At the lower end of the recording tool 6 is mounted a caliper arm assembly, Figs. 2, 3b, 4b, ll, 12, and 13. This assembly includes the caliper arms 8 pivoted at their upper ends on pins 8a secured in a mounting web 8b, the latter being attached to the lower end of the recording tool 6 by screws 8c. Each arm 8 has a cam surface 8d against which a cam follower 7 is pressed by its associated spring .9, the spring not only maintaining the follower 7 in contact with the cam 8d but also yieldably urging the associated arm 8 outwardly to contact the bore B as shown in Fig. 2. The lower end of each arm is provided with -a tip 8e rounded on one side to contact the bore B and having an inwardly extending projection 8 these projections nesting together to .mutually support the arms 8 when the latter are retracted together as shown in Figs. 3b and 13. In such retracted position, the feeler arms 8 and the tips 82 are of such composite diameter and shape as to readily enter the tapered opening T and pass through the hole H in the bit D, said arms 8 and tips 82 having been held retracted by the inner wall of the pipe string during the passage of the recording tool therethrough.

At the upper end of the system of ducts, Fig. 4, is a plug 11 adapted to confine the liquid within the ducts and having a screw 11a in a tapped hole through which the liquid may be replenished and through which air may be removed from within the ducts. The plug 11 also has a bore 11b through which a hollow recording shaft 12 passes, the shaft being attached at its lower end to the recording piston and carrying at its upper end a recording stylus 1211. This shaft also has a small breather port 12b communicating through the center of the shaft 12 with a duct 10a so as to vent the chamber 1617, which chamber is normally free of liquid.

The chart chamber 6s houses the data-recording mechanism and has an access door 6p to permit installation or removal of the charts C from the chart rollers l3 and 13a. It will be noted in Fig. 5 that the chart C travels from the roller 13 around the idler rollers 13c and 13d and on to the takeup roller 13a, the stylus 1201 recording the various positions at any particular instant of time by marking the chart C against the idler roller He, the stylus being at all times spring-loaded by the leaf spring 12d. A groove 6x is provided in the door 6p and supports the upper end 120 of the shaft 12, Fig. 5.

A drive wheel 14 is supported on bearings Ma, fixed to leaf springs 14b which springs force the rubber roller 14 against the chart rollers 13-l3a. The rubber roller 14 is driven through a flexible cable 140, which in turn is driven by a series of gears 14d, one of which is driven by a clock mechanism 15 (shown only schematically).

The engagements between the various parts of the recording tool and between the various parts of the swivel support are provided with annular grooves adapted to receive rubber O-rings R to prevent seepage of the various fluids through the joints with which these rings are associated.

Operation With a suitable survey bit D attached to the lower end of the drill string, the operator proceeds to drill the bore B into the earth, and when he has drilled the bore to its desired depth he retracts the drill string upwardly a few feet from the bottom of the bore B, opens the kelly joint and inserts the recording tool and associated swivel support into the pipe string. He then closes the kelly joint and starts the pumps to pump the assembly downwardly within the pipe string S so that the assembly arrives in the relative position shown in Fig. 2.

At this time the ring 3b will have blocked the hole H through the bit D and the pump pressure will suddenly rise. When the pressure has risen to a level suflicient to break the shear pins 2, the piston 1h will be freed to drop to the bottom of the cylinder is and restore circulation in the pipe string S through ducts la and This rise and fall of the pressure will inform the operator of the seating of the caliper in the bit and the operator will then commence withdrawal of the pipe string from the bore. Generally the string will be withdrawn in stands of approximately three lengths of pipe each, and as the string is withdrawn upwardly the feeler members be on the lower ends of the caliper arms 8 will contact the walls of the bore B and be moved inwardly and outwardly according to the various diameters thereof encountered. The inward and outward pivoting of the arms 8 causes axial upward or downward motion of the cam followers 7 and the associated pistons 7a and 70. Axial fluctuation of the location of these pistons causes the volume of liquid within the respective bores 6d and 6k to fluctuate in accordance with the instantaneous summation of the displacement of each of the three groups of pistons, thereby driving the recording piston 10, shaft 12 and stylus 12a upwardly and downwardly with respect to the chart C.

As stated above, the chart is moved by the chart rollers 13 and 13a, rotated by the clock mechanism 15; and as the drill string is removed, stand by stand, the chart C will show the summation of the instantaneous deflections of the various caliber arms 8.

Moreover, each time that the upward travel of the drill string is interrupted for the purpose of unscrewing a stand of pipe, the chart C will indicate a straight line during the interval that the stand is being unscrewed, since the caliper arms 8 will be standing still with respect to the walls of the bore at that time.

As a tool joint is unscrewed and the drill string accordingly lowered in the bore B by the length of the threads on the tool joint, the swivel support may telescope upwardly within the fluid passage P of the drill string S to prevent bending or breaking of the caliper arms 8. It should also be noted that the pipe string S and associated survey bit D may be freely rotated with respect to the measuring tool and caliper arms, since the swivel support is supported from above only by the ring 3 and ball bearings 3a. As the pipe string is rotated or lowered, therefore, the caliper arms 8 stand still within the bore, thereby preventing damage thereto.

By inspection of Fig. 3 it will be apparent that the ducts lie and 1d and the cylinder 10 form openings communicating the Well bore B with the fluid passage P of the drill string, thereby permitting circulation of the drilling mud through the string at all times so that the operator will have suflicient control to prevent blowouts.

When the drill string has been entirely removed from the well the marked chart may be removed from the tool 6 and may be replaced by a new chart simply by unscrewing the upper casing 611 from the lower casing 6v of the recording tool 6 and by opening the door 6p which leads into the chart chamber, Fig. 4.

We do not limit our invention to the exact form shown in the drawings, for obviously changes may be made therein within the scope of the claims.

We claim:

1. A well diameter caliper to be introduced into the bottom of a drilled bore through the fluid passage of a drill string and survey bit comprising, a body; a plurality of axially disposed annularly spaced caliper arms pivoted at their upper ends to the lower end of said body, said arms each having a cam surface at its upper end; a plurality of cam followers each reciprocably mounted in a cylindrical bore in the lower end of the body and contacting one of said cam surfaces; a measuring piston in each cylindrical bore connected for unitary axial displacement; with its associated cam follower, each measuring piston dividing each cylindrical bore into upper and lower portions, the respective upper portions being interconnected and the respective lower portions being interconnected; a recording piston movably mounted in a recording cylinder, said upper portions being connected with the upper end of said recording cylinder, and said lower portions being connected with the lower end of said recording cylinder; hydraulic liquid filling said recording cylinder and said upper and lower portions; a chart; means for mounting and driving the chart; and a recording stylus engaging said chart and linked to said recording piston, said stylus being moved thereby in proportion to the instantaneous average displacement of said measuring pistons; means for yieldably urging said arms to pivot outwardly and contact the well bore; and means for suspending said caliper below said bit adjacent its fluid passage.

2. In a device as set forth in claim 1, said suspending means comprising a supporting member fixed to the upper end of said body; an annular ring around the upper end of said member and journaled thereon by antifriction bearing means, said fluid passage through said bit having a shoulder therein and said ring being larger in diameter than said shoulder whereby the ring will seat on the shoulder and rotatably suspend the member and body; and duct means through said member communicating said fluid passages with said well bore.

3. A well diameter caliper to be introduced into the bottom of a drilled bore through the fluid passage of a drill string and survey bit comprising, a body; a plurality of axially disposed annularly spaced caliper arms pivoted at their upper ends to said body, said arms each having a cam surface; a plurality of cam followers each reciprocably mounted in a cylindrical bore in the body and contacting one of said cam surfaces; a measuring piston in each cylindrical bore connected for unitary axial displacement with its associated cam follower, each measuring piston dividing each cylindrical bore into upper and lower portions, the respective upper portions being interconnected and the respective lower portions being interconnected; a recording piston movably mounted in a recording cylinder, said upper portions being connected with the upper end of said recording cylinder, and said lower portions being connected with the lower end of said recording cylinder; hydraulic liquid filling said recording cylinder and said upper and lower portions; a chart; means for mounting and driving the chart; and a recording stylus engaging said chart and linked to said recording piston, said stylus being moved thereby in proportion to the instantaneous average displacement of said measuring pistons; means for yieldably urging said arms to pivot outwardly and contact the well bore; and means for suspending said caliper below said bit adjacent its fluid passage.

4. In a device as set forth in claim 3, said suspending means comprising a supporting member fixed to the upper end of said body; an annular ring around the upper end of said member and journaled thereon by antifriction bearing means, said fluid passage through said bit having a shoulder therein and said ring being larger in diameter than said shoulder whereby the ring will seat on the shoulder and rotatably suspend the member and body;

and duct means through said member communicating.

said fluid passages with said well bore.

5. A well diameter caliper to be introduced into the bottom of a drilled bore through the fluid passage of a drill string and survey bit comprising, a body; a plurality of axially disposed caliper arms pivoted at their upper ends to said body, said arms each having a cam surface; a plurality of cam followers each reciprocably mounted in a cylindrical bore in the body and contacting a cam surface; a measuring piston in each cylindrical bore connected for unitary axial displacement with its associated cam follower, the respective cylindrical bores being interconnected; a recording piston movably mounted in a recording cylinder, said cylindrical bores being connected with said recording cylinder; hydraulic liquid filling said recording cylinder and said cylindrical bores; a chart; means for mounting and driving the chart; and a recording stylus engaging said chart and linked to said recording piston, said stylus being moved thereby in proportion to the instantaneous average displacement of said measuring pistons; spring means yieldably urging said followers against said cams to urge the arms to pivot outwardly and contact the well bore; and means for suspending said caliper below said bit adjacent its fluid passage.

6. In a device as set forth in claim 5, said suspending means comprising a supporting member fixed to the upper end of said body; an annular ring around the upper end of said member and journaled thereon by antifriction bearing means, said fluid passage through said bit having a shoulder therein and said ring being larger in diameter than said shoulder whereby the ring will seat on the shoulder and rotatably suspend the member and body; and duct means through said member communicating said fluid passages with said well bore.

7. A Well diameter caliper to be introduced into the bottom of a drilled bore through the fluid passage of a drill string and survey bit comprising, a body; a plurality of caliper arms supported by said body; measuring means in said body and operatively connected with said arms for averaging the displacements thereof; means for recording the instantaneous average displacement of said caliper arms; means for yieldably urging the outer ends of said arms outwardly to contact the well bore; and means for suspending said caliper below said bit adjacent its fluid passage.

8. In a device as set forth in claim 7, said suspending means comprising a supporting member fixed to the upper end of said body; an annular ring around the upper end of said member and journaled thereon by antifriction bearing means, said fluid passage through said bit having a shoulder therein and said ring being larger in diameter than said shoulder whereby the ring will seat on the shoulder and rotatably suspend the member and body; and duct means through said member communicating said fluid passages with said well bore.

9. A well diameter caliper to be introduced into the bottom of a drilled bore through the fluid passages of a drill string and survey bit comprising, a caliper tool of diameter small enough to pass through said fluid passages; and a swivel support comprising a supporting rod fixed at its lower end to a universal joint which in turn is fixed to the upper end of said tool; an annular ring around the upper end of the rod and journaled thereon by antifriction bearing means, said fluid passage through said bit having a shoulder therein and said ring being larger in diameter than said shoulder whereby the ring will seat on the shoulder and rotatably suspend the support and recording tool; and means for indicating the seating of said ring on said shoulder.

10. In a device as set forth in claim 9, said rod having a cylindrical bore extending downwardly into its upper end and communicating by ducts through the side of the rod below said ring, and said indicating means comprising a piston in said cylindrical bore; and shearpin means normally retaining said piston in said bore above said ducts whereby the piston will close the passage through the support formed by the bore and ducts until the ring seats and the fluid pressure in the passages rises high enough to shear the pins and permit the piston to fall below the ducts and open said passage through the support.

11. A well diameter caliper to be introduced into the bottom of a drilled bore through the fluid passages of a drill string and survey bit comprising, a caliper tool of diameter small enough to pass through said fluid passages; and a swivel support comprising a supporting rod fixed at its lower end to said tool; an annular ring around the upper end of the rod and journaled thereon by antifriction bearing means, said fluid passage through said bit having a shoulder therein and said ring being larger in diameter than said shoulder whereby the ring will seat on the shoulder and rotatably suspend the support and caliper tool; and duct means by-passing said ring and communicating said bore with said fluid passage.

12. In a device as set forth in claim 11, said duct means passing through the upper end of said rod and through the side of said rod below said annular ring; and frangible plug means sealing said duct means to cause a sudden pressure rise in said fluid passages when said ring seats to indicate the seating thereof, said plug being subsequently moved clear of the duct means by the pressure to restore fluid circulation through the drill string.

13. A well diameter caliper to be introduced into the bottom of a drilled bore through the fluid passages of a drill string and survey bit comprising, a caliper tool of diameter small enough to pass through said fluid passages; and a support comprising a supporting rod fixed to said tool; a universal joint in said rod; an enlargement at the upper end of the rod, said fluid passage through said bit having a shoulder therein and said enlargement being larger in diameter than said shoulder whereby the enlargement will seat on the shoulder and suspend the support and caliper tool; and duct means by-passing said enlargement and communicating said bore with said fluid passage.

14. In a device as set forth in claim 13, said duct means passing through the upper end of said rod and through the side of said rod below said enlargement; and frangible plug means sealing said duct means to cause a sudden pressure rise in said fluid passages when said enlargement seats to indicate the seating thereof, said plug being subsequently moved clear of the duct means by the pressure to restore fluid circulation through the drill string.

15. A well diameter caliper to be introduced into the bottom of a drilled bore through the fluid passages of a drill string and survey bit comprising, a recording tool of diameter small enough to pass through said fluid passages, caliper means on said recording tool operatively associated with a recording mechanism within said tool; and a swivel support comprising a supporting rod fixed at its lower end to a universal joint which in turn is fixed to the upper end of said tool; an annular ring around the upper end of the rod and journaled thereon by antifriction bearing means, said fluid passage through said bit having a shoulder therein and said ring being larger in diameter than said shoulder whereby the ring will seat on the shoulder and rotatably suspend the support and recording tool; and means for indicating the seating of said ring on said shoulder.

16. In a device as set forth in claim 15, said rod having a cylindrical bore extending downwardly into its upper end and communicating by ducts through the side of the rod below said ring, and said indicating means comprising a piston in said cylindrical bore; and shearpin means normally retaining said piston in said bore above said ducts whereby the piston will close the passage through the support formed by the bore and ducts until the ring seats and the fluid pressure in the passages rises high enough to shear the pins and permit the piston to fall below the ducts and open said passage through the support.

17. As an article of manufacture, a rod having a bore extending inwardly into one end; an annular ring around said end of the rod and journaled thereon by antifriction bearing means, said rod having ducts communicating through the side of the rod with said bore, the ducts being on the opposite side of the ring from said end of the rod; and frangible means for blocking the passage formed by said bore and said ducts.

18. As an article of manufacture, a calipering and recording tool comprising, a body; a plurality of axially disposed annularly spaced caliper arms pivoted at their upper ends to the lower end of said body, said arms each having a cam surface at its upper end; a plurality of cam followers each reciprocably mounted in a cylindrical bore in the lower end of the body and contacting one of said cam surfaces; a measuring piston in each cylindrical bore connected for unitary axial displacement with its associated cam follower, each measuring piston dividing each cylindrical bore into upper and lower portions, the respective upper portions being interconnected and the respective lower portions being interconnected; a recording piston movably mounted in a recording cylinder, said upper portions being connected with the upper end of said recording cylinder, and said lower portions being connected with the lower end of said recording cylinder;

hydraulic liquid filling said recording cylinder and said upper and lower portions; a chart; means for mounting and driving the chart; and a recording: stylus engaging said chart and linked to said recording piston, said stylus being thereby moved in proportion to the instantaneous average displacement of said measuring pistons; and means for yieldably urging said arms to pivot outwardly of said body.

19. In an article as set forth in claim 18, each caliper arm having a rounded tip member at its lower end; and each tip member having a projection extending radially inwardly with respect to the axis of the body, said projections nesting against each other to support the arms when the latter are aligned with said axis, said tip members forming a composite centralizer when the arms are so aligned.

20. As an article of manufacture, a calipering and recording tool comprising, a body; an annular series of caliper arms pivoted at their inner ends to said body, said body having a cylindrical bore in the vicinity of each caliper arm; a measuring piston in each cylindrical bore connected for axial displacement by its associated caliper arm, each measuring piston dividing each cylindrical bore into inner and outer portions, the respective inner portions being interconnected and the respective outer portions being interconnected; a recording piston movably mounted in a recording cylinder, said inner portions being connected with one end of said recording cylinder, and said outer portions being connected with the other end of said recording cylinder; hydraulic liquid filling said recording cylinder and said inner and outer portions; a chart; means for mounting and driving the chart; and a recording stylus engaging said chart and linked to said recording piston, said stylus being moved thereby in proportion to the instantaneous average displacement of said measuring pistons; and means for yieldably urging said arms to pivot outwardly of said body.

21. The method of calipering a well bore through the opening through a survey bit during withdrawal of the drill string and bit from the bore, including the steps of lowering a calipering and recording tool downwardly in the drill string after the completion of the drilling operation; suspending the tool through the lower end of the survey bit; and withdrawing the drill string, bit and tool upwardly of the well bore while simultaneously recording in the tool the calipered Well diameters.

22. The method of calipering a well bore through the opening through a survey bit during withdrawal of the drill string and bit from the bore, including the steps of lowering a caliper downwardly in the drill string before withdrawal thereof from the well bore; suspending the caliper through the lower end of the survey bit; and withdrawing the drill string, bit and caliper upwardly of the well bore while simultaneously calipering the latter.

References Cited in the file of this patent UNITED STATES PATENTS 1,981,665 Rieber Nov. 30, 1934 2,102,080 Kinley Dec. 14, 1937 2,232,360 Barnett Feb. 18, 1941 2,341,228 Moore Feb. 8, 1944 2,348,192 Chambers May 9, 1944 2,395,137 Millikan Feb. 19, 1946 2,524,031 Arps Oct. 3, 1950 2,567,548 Chaney et a1. Sept'. 11, 1951 FOREIGN PATENTS 7,196 Great Britain Mar. 27, 1903 

